MCAT Nephron questions with correct answers rated A+

MCAT NephronProximal convoluted tubule (1) - correct answer permeable to amino acids, glucose, water-soluble vitamins, and salts, which are reabsorbed with water. Filtrate is isotonic to interstitium. Vasa recta - correct answer capillary bed that removes substances from interstitium to be returned to systemic circulation Descending loop of Henle(2a) - correct answer Water-permeable; as interstitial concentration increases, water flows out of this structure. Ascending loop of Henle (2b) - correct answer Permeable to salts; as interstitial concentration decreases, more salt is removed from the filtrate. Distal convoluted tubule (3) - correct answer Responds to aldosterone to promote sodium reabsorption, pulling water with it Collecting duct (4) - correct answer Collects urine before excretion; responds to ADH and aldosterone; anything that is left in this structure is excreted Medulla - correct answer inner core of nephron Cortex - correct answer outer layer of nephron Aldosterone - correct answer Steroid hormone; Increases reabsorption of ions and thus water in the distal convoluted tubule (raises blood pressure) ADH/vasopressin - correct answer peptide hormone; synthesized by hypothalamus; released by posterior pituitary in response to high blood osmolarity allows more water to be reabsorbed by making cell junctions of the collecting duct leaky. Inhibited by caffeine and alcohol (which make you excrete dilute urine frequently) Bicarbonate buffer system - correct answer CO2 + H2O -- H2CO3 -- H+ + HCO3- Renin pathway - correct answer decreased bp stimulates release of renin from juxtaglomerular cells; angiotensin is cleaved to angiotensin I and converted by angiotensin-converting enzyme to angiotensin II -- this promotes release of aldosterone.